Automatic telephone system.



c. s WINSTON..

-AUTOMATIC TELEPHONE SYSTEM.

APPLICATION FILED FEB. 19, 1913.

Patelited Febi20,1917.

3 SHEETS-SHEET 1.

C, S. WINSTON.

7 AUTOMATIC TELEPHONE SYSTEM.

APPLICATTON FILED FEB I9, T913- Patented Feb. 20,1917.

3 SHEETS-SHEET 2.

C. S. WINSTON.

AUTOMATIC TELEPHONE SYSTEM,

APPLICATION FILED FEB. 19. I913.

Patented Feb. 20', 1917-.

3 SHEETS-SHEET 3} D ET/ 5 4 TENT oFFIoE.

'Y/HARLES s. WINSTON, or CHICAGO, ILLINoIs AssIGNoR T KELLOGG swIToHBonRn AND SUPPLY COMPANY, or CHICAGO, ILLINOIS, A CORPORATION or ILLINOIS.

AUTOMATIC TELEPHONE SYSTEM;

Specification of Letters Patent. Patented Feb. 20, 1917- Application filed February 19; 1913. Serial No. 749,324.

To ((Zl/C/LOITZ it may concern:

Be it known thatI, timnnns S. lViNsToN, aciti /Len of the United States of America, residing in Chicago, county of Cook, and State of Illinois, have invented certain new .aud usei'ul Improvements in Automatic 'lelephone Systems, of which the following is a specification.

My invention relates to telephone systems and has to do more lmrticularly with metallie line or lwowvire control circuits for con trolling the operation of selective switches. In the so-called metallic circuit automatic telephone systems, wherein two-dimension switches are employed,'and in which primary and secondary circuit changes are effected, means must be provided which eit'ect a secondary circuit change after the transmission of the primary impulses, such means remaining in a certain condition during .the ti'ansn'iission of the primary impulses and thereafter automatically operated to effect this secondary circuit change. In systems of this character a release controlling device as a-release relay must also be provided which is not aii'ected by the transmission of the primary impulses at a predetermined period, but when the metallic 'eircuitis interrupted for any appreciable period this release relay. must operate to effect, the restoration of the switch. To this end I have provided diiferential secondary and release relays which do not respond to short periodic current variations of a predetermined period, such as the transmission of the primary impulses, but will respond-only to a longer current variation to bring about the socalled secondary and release circuit changes.

In the, accompanying drawings I have illustrated a preferred embodiment of my invention the like parts of these drawings being indicatedby likereference characters and in which l igure 1, comprising Parts 1, 2, and 3, illustrates an automatic telephone systemcmbodying my invention;

Fig. 9 illustrates diagrammatically a switch construction adapted for use with the individual line switch of the system shown;

Fig. 3 is a diagrammatic view of the contact bank and wiper arran ement of the selector and. connector switc es.

" In illustrating my invention I have shown be'operated to pick out an idle connector E which has access to the line of a called substation F. A line switch B is alsofsho'wn' associated with the called substation F. By placing Fig. 1, Part 2 between Fig, 1, Part 1, and Fig. 1 Part 3, the description of the system may be more readily followed. I

preferably 'employ hundred point selector and connector vswitches,'and also provide ten per cent. trunking in accordance with the common practice of the present day, and in a 10,000 line system as illustrated, on the ercenta 'e. of trunkin referred tothere I '5 b would of course be 1000 first selectorshl,

1000 second selectors Djand 1000 connectors E. A line switch Bis of course provided for each line and'I preferably divide the lines into groups of 100 and for each such.

group 10 first selectors O are provided;

'lhei-efOre the line switches B are preferaa.bly 10 point switches, each group of 100 such switches being multiply connected to 10 corresponding first selectors C although in the illustration but two such multiple connections are shown. Thesecond selectors. D

and connectors E are distributed in accord-.

out-

ance with the ten per cent. trunkin lined and it thought that this distribution oi these switches is so well known thatfurther reference-thereto is unnecessary,

Referring now more in general to the apparatusJot' my preferredarrangement, sub-.

stations as A of any well-known common battery type may be provided and a calling. device 1 is also. provided for each'substation. such calling device being of the metallic line type which when operated will interr t the metallic circuit of the line from one to ten times as desired. Substation A is connected by line conductors 2, 3, to the line switch B at the central office said switch comprising a line relay LR which is energized u on initiation of a call toenergize a cut-oil relay CO. A-mothr' magnet M is also provided which has its. circuit closed through the line and cut-oil relays and is adapted to advance the wipers l, 5, 6 in a step by step movement over the associated ten sets of contacts 7, 8, 9. An extra set of contacts 10, 11, 12 are preferably provided for the line switch B so that'if all of the trunks extending from the contacts 7, 8; 9, are busy the switch will step to the last setbf contacts and transmit a busy signal to the calling substation, in which case the receiver may be replaced upon the switchhook thereat to effect the restoration of the An oil-normal contact @N is' line switch. alsoprovided which is adapted to move to an alternate position upon the first step of the wipers and'remain in its alternate position until the wipers are again restored. to normal.

In Fig. 2, I have illustrated diagrammatically a mechanical structure adapted for operation with the line switch circuit 13, the like parts being indicated by like reference characters. In this construction, holdin p'awls 13, 14 are provided for the line and. cut-oil relays, the pawl 13 being normally free of engagement with the driving ratchet 15 while pawl let is normally in engagement with said ratchet. During the selecting operation of the line switch both of the relays CO and LR are energized so that the pawl 13 is in engagement with the ratchet 15 while the pawl 14 is out of engagement therewith. As soon as an idle trunk is selected, the cut-oil relay CO deenergizes and the line relay LR remains energized so that both of the pawls 13, M are engaging the ratchet wheel. Now when a release of, the

switch is desired, the cut-off relay CO is again energized and the line relay LR main- -tained energiied so that both of tlie holding paw'ls are disengaged. and therefore the "wiper-sure free to be restored to normal by spring tension.

' il he'selector and connector switches preferably employed are of thetwo-dimension type, that is the type. in which the bank contacts are divided into groups and in which a primary adjustment of the switch is effective to select a group and thereafter a secondary adjustment produced to select a contact of the selected group. On a basis of ten per cent. trunking. this means that the contacts are preferably divided intoten groups of ten contact sets each as is diagrammatically illustrated in Fig. As all of the selector and connector switches are of the same type it might be well to describe in general the construction and op eration of these switches before proceeding with a description of the circuits.

in Fig. 3, l have illustrated diagrammatically the preferred contact bank and wiper arrangement of the selector and connector switches each set of three contacts 16, 1?, l8

ers 19, 20, 21, as shown at first selector C as of the first selector C being indicated by a single piece marked 16, 17, 18. These contact pieces are divided into ten arcuate radially disposed rows and a set of three wipare adapted for cooperation with the bank 76 contacts. In order to give the wipers their primary adjustment, a primary shaft PS is pro ided which is adapted to be rotated by a primary magnet (PM of the circuit draw ing) and thereafter the secondary shaft. SS is moved downward by a secondary magnet (SM of thecircuit drawing) to give a secondary adjustment of the-wipers to select a set of contacts of the selected row. A pri 5Q mary'ofi-normal switch PON is also provided which is moved to its a'lternateposition. upon the first primary step of the switch and a secondary oil-normal switch SON is also provided which is adapted to be moved to its alternate position upon the first secondary step of the switch. The primary and secondary adjustment of the switch is against the tension of a pair of spring members and therefore holding as pawls are also provided. I

In the preferred switch construction I do not depend upon a release magnet for withdrawing the retaining pawls but preferably employ a releasing arrangement in which the secondary magnet is again brought into play to advance the wipers in a continued secondary adjustment over. the contacts or the selectedrow until they have passed beyond the last contact of the 10s group. Upon reaching this-point the wipers are automatically restored by spring ten sion over a path indicated by the dotted' line 222 of Fig. 3 and in the direction of the arrows indicated thereon. Thus in a we complete cycle of operation of the wipers the contact ends follow a path as illustrated by this dotted line222 but of course in ac cordance with the selected row. In the restoring operation of the switch the primary 11 9 and secondary off-normal switches are also restored in a manner as will be clear from Fig.3. It is thought that from the above description the operation of the preferred selector and connector switch construction 11 First selector-0.

Each first selector C is provided with sets of contacts 16, 17, 1'8, and cotiperating wipers 15), 20, 21, test wiper 19 having g its contacting end so arranged that it will make one contactlti before leaving the preceding contacts while the line wipers 20. 2-1, are arranged to break before make. A.

primary magnet PM; is provided for giving though other forms of .ing 24 of the release relay,

the primary adjustment to the wipers and -a secondary magnet SM provided for giving the secondary adjustment to these wipers, the secondary magnet being preferably operated by alternating current from an alternating current generator as shown alloperating current may be employed. An impulse relay IR .is bridged across the line conductors at first selector C and is adapted to be energized by current flowing over-the calling line when the selector C is connected with. A main release relay MRR is also provided which is preferably energized responsive to the initialenergization of IR, and upon the energization of MRR, a differential release relay RR its upper winding so that its alternate contact 22 closes. This establishes a locking circuit for RR and also for relay MRR. Now when the impulse relay IR is rapidly operated for transmitting primary impulses, a circuit is closed through the lower windthe flow of current through this lower winding being opposite to that of the upper winding '23, this action tending to neutralizethe magnetism of the core of RR but these impulses through the lower winding 24 are of too short a duration to sufficiently neu tralize the relay to cause the falling back of its armature. That is, as long as relay IR israpidly vibrating at a predetermined rate, these impulses do not effect a retrac tion of the armature of RR, but as soon as relay IR is deenergized for a predetermined longer period than when operated for sending primary impulses, the neutralizing effect, of the winding 2% is sufficient to cause a retraction of the armature of RR and thereby a release of the main release relay MR-Il which brings about the restoration of switch C.- As relay IR is not deenergized forsuch a releasingperiod except when the receiver is replaced, it is apparent that both of the relays MRR'and RR maintain their armatures attracted until a release is desired.

Now as to the secondary circuit changes which follow each series of primary impulses, I have provided a differential secondary relay SR which has a circuit closed through its two windings 25, 26, when relays IR and RR initially attract their armattires. Therefore the secondary relay SR does not attract its armature because the flow of current through its two windings 25, 26, has a differential effect. upon the magnet thereof, but as soon as the relay IR starts to vibrate in response to the operation of the calling device at the substation,

the circuit through one' of the windingsyin this instance winding 25, is interrupted each time relay IR vibrates and upon the first vibration of relay IR the How of current is energized by current through normal switches FUN and preferably employed, they also connection 'through the winding is being rapidly interrupted.

As soon as relay SR stops which is at the tern'unation of vibrating, t1 t 1e clrcm the calling device operation, through the winding of relay closed long enough to effect a neutralization of the magnet of relay SR so that the armature of this relay retracts .and brings about thesecondary operation of the switch through a test relay T which energizes at this time.

I also provide primary and secondary off- SON respectively which operate in a manner as already described.

I also preferably. arrange the impulse and secondary relays to act as repeating relays,

that is these relays are also adapted for transmitting prnnary and secondary impulses to the other selector and connector switches for causing their operation as will be more particularly described.

Now as to the second selector switches I) comprise primary and secondary magnets PM, SM,- a test relay T and a release relay RR, which relay RR tion'of the switch I) and remains energized until restoration is desired. The primary and secondary off-normal switches ,ION,

selectors is the same as referred to in connection with Fig.

.Various types of connector switches'may be employed in connection withmy in'\en tion but for the purpose of illustration I employ a connector switch E of a type of switch mechanism similar to that outlined in Fig. Therefore primary and secondary magnets IM and SM are provided for operating the switch. A release relay RR is also provided which is energized upon made with the connector E. Another release relay RR is also provided which is brought into play, when a release of the connector is effected. In order to disconnect the primary magnet and connect the secondary magnet in operative re- ,lation with the line following the transoperated to drive the switch into connection with the terminal of the called line SR remains of the second selectors operate in a energizes upon the seleclat after which another switching relay SW is operated responsive to the last secondary circuit change. If the called line is busy the busy relay BR which hadpreviously t5 been energized, restores to connect the busy back device BB in'circuit with the calling substation. line test relay LT is energized to bring about the operation of the interrupter relay IR which connects the ringing generator RG in circuit with the called line. Upon a re sponse being received from the called substation, 'a control relay GB is energized as is also the closing relay CL and disconnect relay DR whereby the ringing current is disconnected from the called line.

I have preferably arranged the release of the switches used in establishing a connection so that if a call is completed, the line switch B first selector C and secorid selector D are restored by the act of the callingv subscriber replacing his receiver and the I release of theconnector E brought about by the restoration of the receiverat the called substation. If the connection is extended to the called line and the called subscriber fails to-respond, all of the switches used in establishing the connection are brought to normal by the replacing of the 330 receiver at the calling substation. Also should the calling subscriber fail to extend the connection to the terminals of the called line, any switches which may have been operated may be brought to normal by'the substation.

Opemzfzon.

Having described in general the appa- 40 ratus employed in the preferred embodiment of my invention the operation of the system illustrated in extending a connection will now be described more in detail. As--.

su'ming now that a connection is to be made between calling substation A and the called substation F, the number of whose line-we will assumeis 2343 the calling subscriber removes the receiver at substation A, A circuit for the line relay LR is thus established from battery through the winding thereof, wiper 6, normal contact 27, line conductor 2, substation A, line conductor 3,-i1ormal contact 28, wiper 5, to grounded contact-29. l-telay LR therefore energizes closing its alternate contact to establish an energizing circuit for the cut-off relay CO traced from ground at said alternate contact 30, normal contact ON, the winding of CO tobattery,

, Relays LR and CO being energized, a cir- 60 cuit for motor magnet M is of course established from the alternating current generator connected to the winding of M, the alternate contact 31 to ground at alternate contact 52. hi um M therefore advances t5 the wipers i, 5, a vnto engagement with the test contact 7 in a, manner as will be p CO and LE, 3, locking circuit for t. If the called line is idle the first idle one, and which contact 1 ter'y thro ugh the left hand winding there restoration of the receiver at the calling first set pf contacts 7, 8, 9, which if bus have a ground potential connected. to

entlydescribed. Therefore due to the clc ing of alternate contacts 32, 33, of rc lays is established through the test so that the motor magnet M advanc wipers a step and into engagement with ti next set of contacts and in tact cont-inn this operation as long as the wiper l is on ing busy contacts 7. Upon reaching their set of contacts, which we will assume the first selector C shown, there hcin. ground or b'usy'potential upon the test c tact ofthis set, the locking circuit for H lays CO and LR is interrupted and re CO being a quick relay immediately tracts its armature While the line relay L which is a slow acting relay lllOlllQllili-.r maintains its armature attracted. soon as the relay CO retracts and closes its use 'mal'contactsQ'T, 28, the impulse relay energizes by current over the calling line and immed ately closes a locking circuit tc maintain the armature of the relay Lit tracted. This energizing circuit tor impulse relay IR may be traced from contact 8, wiper 5, normal contact 28, in conductor 3, substation A, hue conrhictor it, normalcontact 27, wiper (3 and contact 9 and then through the right hand win fling of IE to ground. Relay IR therefore gizes closing its alternate contact 33 which connects ground from the normal contact 3 10f PO N, alternate contact 83 and. the

winding of MRR to battery which immediately energizesv and closes its alternate contact 35 to apply this said ground through test contact '7 and wiper t, alternate contact 32 and winding of LE to battery. 'lhus relay- LR being maintained energized, the Wipers of the line switch B are held in their l '1 operated position.

The initial energization of the impulse relay IR through the assistance of the main release relay MRR closes a circuit through the winding 23 of release relay liit due the closing of alternate contact 36 of HRH. This circuit through the winding 23 of ER causes the energization thereof and the at traction of its armature whereby its a lternate contact 29. is closed establishing a loclring circuit forboth of the release relays MRR and RR. These relays now maintain their armatures attracted until a releaf deiinergization of the impulse relay, w del nergization is only brought about wn a release is desired and the receiver 13: placed upon the switch-hook.

Also responsive to the op three relays IR, than, and I closed through eachoi the wire:

cr-i on or circuits through these windings 25, 26 have adifferential effect upon the magnet of SR so that the armature thereof is not attracted. The circuit through the upper winding may be traced from battery through said winding to ground at alternate contact 38, while the. circuit through the Winding 26 may be traced from battery through said winding 26, conductor 39, al-

ternate contact 33, to ground at normal contact 34, and after the operation of RE the circuit throu h windin 26 may betraced also to ground. at alternate contact 22. Thus the secondary relay SR does not attract its armature at this time. v

The circuit of the calling line having been extended to an idle first selector C, operation of this selector in extending thecall will now be described. The number of the called substation being 2343, the calling device 1 at substation A is operated to effect two interruptions of the impulse contacts thereof whereby the circuit through the impulse relay IR is interrupted two times causmg two operations of its armature. Respon- I sue to each suchoperation of IR, its normal contact 38 is closed to transmit a. primary impulse through the primary magnet Phi, this circuit being traced from'said grounded normal contact 38, alternate contact 40, 'primary conductor 41, conductor 42, normal contact 43 and the winding of PM to battery, these two operations ofthe primary magnet efi'ecting two primary steps of the 'wipers 19, 20,21 to select the second group of contacts 16, 17, 18. These contacts in accordance with the well-known practice lead to second selectors having access to connector switches associated with lines in the .second thousand group.

Also responsive to the two primary operations of relay IR its normal contact 33 is closed, each such closure effecting a short impulse through the winding 24 of the release relay, but it is to be understood thatthese impulses are not of suiiiclent duration to bring .about a neutralizing eifect of this winding 24 sufiicient to cause a retraction of the armature thereof. g

Now as to .the secondary relay SR, it will -be remembered that its winding 26 is maintained in a closed circuit'through the alternate contacts 22 of relayRR, but upon the first primary operation of relay IR the circuit through the winding 25 of SR'is interrupted for a sufficient period of time so that i't loses its neutralizing efl'ect enough to allow the winding 26 to cause the attraction of the armature of SR and therebythe interruption of its normal contact 44. Although 'this'winding 25 of SR is closed in circuit each time the alternate contact 38 of relay IR operates during the primary operations, these impulses through winding are not suiiicient to bring about a neutralizing efiect to cause av retraction of the ficient tocause a'retractio'n of its armature to bring about this secondary circuit change and thereby the energization of the testrelay T. This energizing circuit for T may be traced from battery through the winding thereof, normal contact 46, alternate contact 47 (which closes upon the first primary step of the switch,) normal contact 44., secondary conductor 48 and the right end winding of l R to ground. The closing of this circuit causes the 'energization of test relay T whereby its alternate contact 49 is closed establishing a circuit through the secondary magnet SM. Magnet SM therefore operates'to advance the wipers 19, 20, 21 into engagement with the first set of contacts 16, 17, 18 of theselected group and assuming this first set leads to a busy second selector, its test contact 16 has a busy' potential connected there to, preferably ground, and. a maintaining circuit forthe test relay is established. This circuit may be traced from said grounded contact 16 ,'wiper 19., alternate contact 50, alternate contact 5'1 and the winding of T to battery. Therefore magnet SM advances the wipers another step and continues this advance as long as the test wiper 19 is engaging busy test 'contacts 16. As soon as an idle set of contacts is reached, (such idle set having no ground or busy potential con nected thereto) the circuit for the test relay T is interrupted whereby it restores interrupting the circuit for SM and rendering the wipers inert. As soon as relay T restores,

its normal contact 50 closes placing a ground or busy potential uponthe test contact 16 of the selected set. This ground connection to the test terminal 16 also-establishes an energizing circuit for the release relay RR of the selected second selector I) this circuit being traced over the conductor 52, normalcontact 53, winding of R11 to'battery energizcalling device 1 at substation A'interrupts the calling line circuit three times, c'orresponding to the second digit of: thefcalled calling line has thus substation'number and thereforetheimpulse rel-1y IR receives three primary op erations. As before the secondary relay SR attracts its armature on the first one of this last set of primary operations of IR and said relay SR maintains its armature attracted until the cessation of these primary operations. Also responsive to the three primary operations of IR three impulses are transmitted to the primary mag net ,PM of second selector D, traced from.

ground. at normal contact-38 of IR, alternate contact 40, primary conductor 41, contact 55,- wiper 20v and contact 17, conductors 57, 58, normal contact 59- and the Winding of PM to battery. 'Magnet PM therefore advances wipers 60, 61, 62, three pri-,

relay T This circuit for T is traced from I ground through the right end winding of 11R, secondary conductor 48, normal contact's 44,56, wip'er'21 and contact 18, secondary conductor 66, conductor 67 alternate contact 68 (which closed upon the first primary step of switch D), normal contact 69 and the winding of T to battery. Test relay T therefore is energized closing its alternate contact 7 0 to establish an operating circuit for the secondary magnet SM.-

whereby the wipers 60, 61, 62, receive a secondary 'adjustment'and are thus advanced by the first step into engagement with the first set of contacts 63, 6st, 65 of the selected group. If this set is busy its test contact GB'h-as a busy potential connected thereto,

preferably ground, as will hereinafter appear. Therefore a maintaining c1rcu1t for the test relay T is provided being traced from grounded test con-tact 63, wiper 60,.

alternate contact 71, alternate contact 172, and the winding of T to'battery so that the test relay is maintained energized over this circuit due to the fact that the initial energizing circuit is interrupted at- SON upon the first secondary step of the switch. The wipers of switch D are thus continued in their secondary adjustment until an idle set of contacts are reached, and due to the fact that'the test contact 63' of an idle set has nobusy potential the maintaining circuit for relay T -is interrupted causing said relay to deenergize and render the wipers inert.

" busy potential, preferably ground is connected through the wiper 60 to the selected test contact 63 rendering all of the multiple contacts connected therewith non-selectable.

I Up'onthe closing of normal contact 71 of T upon lts said deenergization, a

During the secondary travel 01 switcn D the line wipers 61, 62are held disconnected due to the interruption of normal contacts 72, 73, of relay T Thisground connection to the selected test contact 63 also causes the energization of release relay RR "of the selectedconnector switch E this circuit being traced over the test conductor 74, normal contact 75, conductor 76, and the winding of BB to battery. Relay-RR therefore energizes. and is maintained en-- ergized until a release of the connector is effected.

.The calling line circuit has now been extended to an idle connector E which has access to the terminals of the called line and the operation of this connector wil nowbe described.

The subscriber at A now operates his dial 1 for the third time causing fourinterruptions of its impulse springs, corresponding in number to the third digit of the called'line number and the impulse re lay IR therefore receives four primary operations. Responsive to these primary operations the secondary relay SR attracts its armature in a manner as before described maintains it attracted until the cessation of said four primary operations; Also responsive to these four operations of IR four primary impulses are transmitted to the primary magnet PM of connector E, the path of these impulses being traced from ground at normal contact 38 and IR, alternate contact 40, conductor 41, normal contact 55, wiper 20 and contact 17 conductor 57, contact 72, wiper 61 and contact 64:, primary conductor 77, conductor 78,- normal contacts 79, 80, and the winding of PM to battery. Responsive to these four impulses the primary magnet advances wipers 31, 82, 83 to the fourth group of contacts 84, 85, 86 which is the group including theterminals of the called line.

Upon cessation of these primaryoperations of IR, secondary relay SR retrace its armature in a manner as before described I whereby its normal contact '44 is closed and a secondary ,circuit change is-effected to cause the operation of switching relay SW of connector E, the circuit therefor belng'tracecl from ground through the right end wlndmg of IR over the previously de scribed path through the secondary con ductor"66 of switch D, normal contact73, wiper 62, contact 65), secondary conductor 87, conductor 88, alternate contact 89 which closed upon the; first primary step of the connector, normal contact/90 and normal contact 91 of S? through the winding thereof to battery. The switching relay SW therefore energizes closing its alternate contact 92,- establishing a'locking circuit for itself through normal. contact 93 to the grounded test conductor 74. Due-to the interruption of normal contact 79 of SW and i with the primary conductor 77.

Now when the calling device 1 at substation A is operated for the last time to cause three primary operations of the impulse relay IR, secondary relay SR attracts its armature asbet'ore and three impulses are also transmitted IOYCI the primary .conductor along the previously described path to alternate contact 79 of SV, normal contact 91, the winding of SM to battery at.

normal contact 95. Responsive to these three primary impulses the secondary magnet SM advances the wipers 81, 8'2, 83, in a,

secondary direction to select the third set of contacts S-l, 85, 80, which are the terminals of the wanted line. Followin the transmission of the last set of primary impulses, the secondary relay SR retracts its armature 'in a manner as before described \rhereby a secondary circuit change is effected to bring about the operation of switching relay SlVBthis secondary operating circuit being traced over the previ ously described path to secondary conductor 87, conductor 88, alternate contact 90 which closed upon the first secondary step of the switch, normal contact 195 and the winding of 31V to battery. Relay SW therefore closes its locking contact 96 establishing a' locking circuit for itself over conductors 97, 98, to the grounded off-normal contact 99. l v

It will be noted that upon the first primary step of the switch and the closing of its primary off-normal contact 99, a circuit for busy relay BB is established, traced from ground at said alternate contact 99, conductors 98, 97, normal contact 100 and the winding of BR to battery so that relay BR remains energized until its circuit is interrupted at the normal contact 100 by the' energization of the switching relay SVV as just described. Relay BR being a sluggish relay maintains its'armature momentarily attracted and if the line connected with is busy, said relay BB is maintained energized over a circuit as will be described, but if the line connected with is idle no maintaining circuitfor BB .is established so that it.

retracts its armature to transmit a busy signal to the calling substation.

Called line z'cllc.

gizing circuit which 'may be traced from battery through the winding of CO normal contact OX contact 81 and wiper 81, alternate contact 101 (which is still being maintained closed due to the sluggishness of BR) winding 102, conductor 103, alternate contacts 101, conductors 97, 98 to ground at alternate contact 99/ Both of the relays LT and CO 'aretherefore energized the energization of LT causing the closure of its alternate contact 100 whereby the relay H is energized to close its alternate contact 107, which thereby closes another energizing circuitthrough the winding of BR'before ithas had a chance to'v-ntract its armature. Upon theclosing of alacrnate contacts 108, of line test relay LT, the lower winding 102 is short circuited but the upper Winding 109 is connected in a locking circuit'w'hich may be traced from battery through said winding 109, resistance 111, alternate contacts 108, 1.08 conductor 103, alternate contact 104:, 100, conductors 97, 98 to ground at alternate contact 99, this circuit being effective to maintain the relay LT energized until the switchis restored. This shunting of winding 102 is also effective to connect the grounded conductor 10?) through alternate contact 108 and alternate contact 100 to the connected test contact 81 and its multiples, this action rendering these contacts un-selectable by any other switch and also maintaining the cutsofl relay CO energized. Upon said energization of relay H, the control relay GR is connected in bridge ofthe terminals of the called line through alternate contacts 113, 111 of-relay H and normal contacts 115, 116, of interrupter relay IR. Due to the interposition of the condenser at the called substation, this bridge circuit including the control relay CR does not effect an operation of CR until-the re-, ceiver at the called substation is removed as will bemo're particularly described. I

Now as to the application of the-"ringing curreni o the called line, this-is brought about by the closingof alternate contactv 106 of relay LT which connects ground through conductor 117 and normal contact 118 through thewinding of interrupter relay IR, and interrupter I to battery. Due

.to .tlre operation of the interru ter 1, the

interrupterrelay IR alternately ridges the control relay CB and ringing generator RG across the terminals 85, 86, of the called 120 line Each tiine'the ringing generator RG is connected in such bridge through the alternate contacts 115, 116,-ringing current is projected over the calling line and through the call bell at substation F and when the subscriber thereat removes the receiver inresponse'to this call 'and upon the succeeding closure of normal contacts 115,

.116, of IR, an operating circuit for the'conv .trol relay GR is established This circuit v13,1)

may be traced from battery througlr the, upper winding of CR, alternate contact 113,- normal contact 115, wiper 82, terminal 85, line conductor 2, substation F, returning over line conductor 3 terminal 86and wiper 83, conductor. 120, normal contact 116,

alternate contact 1.14. and the lower Winding of CR to ground. This circuit causes the.

relay CR to attract its armature whereby its alternate contact 121 is closed establlshing an energization of closing relay CL -.which in turn causes its alternate contact lease relay RR under control of the called substation because this relay BB cannot now restore as long as the control relay GR. is energized and its alternate contact 126 closed.

Referring again to closing relay CL upon its said energization, its alternate contacts 129, 130 are closed thereby establishing the continuity of the talking circuit between the. two substations A and F this circuit being traced over the heavily marked conductors in which condensers are interposed, the condenser 181 being connected in the secondary conductor at connector E while a condenser 132 is connected in the primary conductor at f rst selector C these condensers pretenting' interference between the battery supply and control relays energized over the. calling and called lines. The substations are now connected for conversation, the talking battery for the calling substation being supplied through the windings of relay IR while the talking battery for the called substation is supplied through the "windings of control relay CR, these relays of course ha-ving a sufiicient: impedance to prevult cross talk 1n accordance with, well known practice.

Disconnection.

After the subscribers have finished conversation, by replacing their receivers upon their respective switch hooks they may effect the. restoration of the switches, the restoration of the receiver at the called substation effecting the restoration of connector E, and the restoration of the receiver at substation i s efi'eeting the restoration of switches B and C and i Assuming now that the subscriber atA is the first to replace the receiver upon its lease deenergization of relay IR a circuit through the lower winding 24 of release resWitch-hook, the circuit for relay IR is lay RR- is established for a suflicient length."

of time to bring about the neutralization of the magnet of RR, this neutralizing circuit being traced from battery through winding 24, alternate contact 135, 33, 35 and alternate contactSl to ground. relay RR retracts its armature causing the interruption of this locking contact 22 and "also of itscontact 135 so that the holding circuit for both of the relays MRR and HR is interrupted rendering the relay RR inert, and causing the retraction of MRR.

Upon said det nergization-of MRR, a release energization of relay T is effected, this 'energizatio'n being over a circuit traced from battery through the winding of T, normal contact 51 to ground at alternate contact 136.

Therefore RelayT therefore closes its alternate contact 49 to establish'a release operating circuit for the secondary magnet SM whereby the wipers are advanced in a secondary direction until they have passed beyond the last contact of the row where they are automatically restored to normal by spring tension in a manner already dcscribed. During restoration of the. wipers, the oil-normal switches are restored so that upon restoration of PON, the circuit for relay T is interrupted causing its restoration and the interruption. of'the circuit of SM. Switch C-is now at normal.

Now as to the restoration of the line switch B, it will be remembered that the relay LR thereof hasbeen held energized over the test conductor and "through alternate contact 34 to ground so that when the swltch PON restored, due to the interruption of alternate contact 34 this holding cir- 'cuit for relay LR is interrupted causing its restoration. Normal contact 30 of LR is therefore closed establishing an energizing circuit for the cut-off relay CO, and relay CO being energized, and LR decnergized both of the pawls 13 and 14 areclear of the ratchet 15- and the yvipers are free to be Re ferring now to the second selector 3,

when the test relay T of first selector Cis energized for release as 'previously described. lhat is when the normal contact '50 of relay T is interrupted during the re lease operation, the holding circuit for release relay RR of second selector I) is interrupted so that this relay restores to estab-' lish a release circuit for the relay T, traced from battery through the. winding of T normal contact 172, to ground at alternate contact 138. Relay-T therefore is euer: gized' to close an operating circuit for magnet SM which advances the wipers of switch I) in a secondary direction and brings about a restoration of the switch in a manner as before described. l pon restoration of FUN, and due to the interruption of its alternate contact 138, the circuit for T is interrupted, causing its restoration whereby the magnet SM is rendered'inert. Switch 1) being at normal is available for use in establishing other connections.

The restoration of connector I) is brought about when the receiver is replaced at' the called substation F'tln's act interrupting the circuit for control relay CR and causingits deenergization. Upon the restoration of CR its alternate contact 121 1s interrupted to allow restoration of relay CL and by the its alternate contacts 94,- 95 whereby the secondarymagnet SM is connected in c1r-.

cuit with thealternating generator and thus the wipers are operated in a secondary direction and restored to normal in a manner as previously described.

Upon the restoration of switch E, the primary cit-normal contact 99 is interrupted causing relay RR to restore and also causing the restoration of DR; The interrup'tion of this circuit at contact 99 also effects the restoration of relay SW Switch E being at normal is available for use in establishing other connections. Called Zine. busy.

when the connector switch connects with a busy called line.

Upon restoraidle. in the operation of the connector, the w apparatus therefor operates the same up to the transmission of the last secondary irn pulse whether the wipers have connected to an idle or busy line, and it Will be remembered that up to this period, that isytheyggtransmission of the last secondary-impulse, that relays RR, BR and SW are energized, the energization of SW" having been eftccted by the last sccondary'impulse. Also due to the closing'bfl alternate contact 100 of a relay SW, the line testrelay LT was con nectedin circuit with the test contact 8450f the called line. This contact now' having a 1 ground potential, the line test relay L'Pis not energized due to the fact tlmt thcre is a ground potential at each of the terminals of its initial energizing winding= .1119 Therefore relay LT doesnot energize and consequently itsassociated= relay H does not busy relay BR- is provided and said relay 1 BR retracts its armature. Upon retraction of the "armature'of BR the test connection to LT is interrupted by the interruptionot contact 101 and due .to the closing of normal contact 150 of BB, the busy back device BB is connected in circuit with the primary conductor to indicate to the calling sub-' scriber that the called line is busy. This busy circuit may be traced from device BB contact 150, alternate contact 80, normal contact 79 to primary conductor 77 folloW- ing the path back over this conductor and through the right end winding of IE to ground' The calling subscriber in response 105 to this signal replaces the receiver upon its switch-hook thereby restoring relay IR and effecting the restoration of the switches G,

B and D as before. In the present instance the. connector switch E is also brought to no normal at the time the test relay T of sec ond selector D energizes for release. That is when this relay T energizes to efiect the release of switch D, its normalcontact 7: is interrupted to. remove the ground connection which maintained the release relay RR ofconnector E energized. It will be noted that due to the fact that no response was secured from a called substation, the 'control of the release relay Rlt remains was not closed. Therefore when relay REP deenergizes andits normal contact 140 is closed, a circuit for ER is-established from .battery through the winding of BB normal contact to ground at alternate contact 99. .RRXtherefore closes its alternate contacts 94, 95, whereby the secondary mag- @et SM is operated to restore the switch E. 1

' Upon the switch E reaching normal the primary off-normal contact 9 is interrupted to allow the deenergization of Eliand SWV All of the switches used in establishing this last attempted connection being at nor mal, are available for main establishing other connections; p

Although I have embodied my invention in preferred circuit arrangements and particular switch constructions, l contemplate the calling line and the control circuits of the first selector may be employed and therefore I do not desire to be limited to the exact structure as shown and described but aim to cover all tlioseeinbodinients as come within the spirit and scope of the appended claims.

lVhat I claim new and desire to secure by United States Letters Patent is:

1. A metallic-line control circuit for automatic switches comprising an impulse relay,

a two conductor operating circuit for said relay and having a call transmitter connected in circuit, means forrapidly operating the impulse relay by said call transmitter for transmitting primary impulses, a diilen 'ential release relay operated responsive to said impulse relay to attract its armature, a locking circuit for said release relay efiective upon its operation, and a neutralizing winding for said releaserelay efi'ective to cause a retraction of its armaure only responsive to an extended denergization of the impulse relay.

2. A metallic-line control circuit for automatic switches'comprising an impulse relay, a two-conductor operating circuit for said relay having a call transmitter connected therewith, means for rapidly operating the impulse relay responsive to said call transmitter fcr transmitting primary impulses,

a differential release relay having an initial operating winding responsive to the initial energization of the impulserelay to attract.

its armature, means for holding said armature' attracted during the primary opera-- 'tions of'the impulse relay, and a neutralizing winding for said release relay'effective to cause a retraction of its armature only responsive to an extended deenergization of the impulse relay.

3. A metallic-line control circuit for anpulse relay, a metallic operating circuit therefor, a call transmitter in said metallic circuit for operating said impulse relay to transmit primary impulses, a differential release relay having an initial operating windiiig closed upon the initial energization of the'impulse relay, a locking circuit including said winding for holding the release relay operated during the primary operatipns of the impulse relay, a neutralizing winding for said release relay adapted to be included i for, a call transmitter connected in said cir cuit, a differential release relay having one of its windings closed responsive to operation of the impulse relay, means for closing a locking circuit through said relay to hold it operated duringthe primary operations of said impulse relay by the called transmitter, a neutralizing winding for said release .rela'y included in an energizing circuit responsive to each primary operation of the impulse relay but not effective to cause a retraction of the armature of the release re- 'lay during such primary operations, said neutralizing circuit being rendered efi'ective to cause a restoration of the armature of the release relay only upon a release deelnergization of the impulse relay.

5. A metallic-linecontrol'circuit for two dimension automatic switches comprising an impulse relay, a two conductor operating circuit for said relay having a call trans-- mitter connected therewith, means for rapidly operating the impulse relay responsive to said call transmitter for transmittingthe primary impulses, a differential secondary relay operated over one of its windings to attract its armature responsive to the firstprimary operation of the impulse relay, and aneutr'alizing winding for said secondary r relay eifective upon cessation of the primary operations of the impulse relay to cause a secondary circuit change following the primary' impulses. I

6. A. metallic line control circuitfortwodimension automatic switches comprising an impulse relay, a two-conductor operating circuit for said relay having a call transnutter connected therewith, means for rap idly operating the impulse relay responsive to said call transmitter for transmitting the primary impulses, a differential secondary tomatic switches comprising a bridged im relay operated to attract its armature refinis er,

dimension automatic switches comprising an impulse relay, a two-conductor operating circuit for said'relay, means'for rapidly operating the impulse relay for transmitting primary impulses, a differential secondary relay operated to attract its armature responsive to the first primary operation of the impulse relay, means for maintaining said armature attracted during the primary operations of the impulse relay and a neutralizing winding for said secondary relay effective upon cessation of the primary operations of the impulse relay to cause a retraction of the secondary armature to effect a secondary circuit change.

8. Ametallic-line control circuit for tw0- dimension automatic switches comprising an impulse relay, a two-conductor operating circuit for said relay, means for rapidly operating the impulse relay for transmitting primary impulses, a differential secondary relay, means for operating said difi'erentia relay to attract its armature and for maintaining said armature attracted during the primary operations of the impulserelay, and a neutralizing winding for said secondary relay effective upon cessation of the primary operations of the impulse relay to cause a retraction .of' the secondary armature to effect a secondary circuit change.

9. A metallic-line control circuit for twodimension automatic switches comprising an impulse relay, a two-conductor operating circuit for said relay, means for rapidly operating the impulse relay for transmitting primary impulses, a differentialsecondary relay, means for operating" said difierential relay to attract its armature and'for maintaining said armature attracted during the primary operations of the impulse relay, a neutralizing winding for said secondary relay efiective upon cessation of the primary operations of thein'ipulserelay to cause a retraction of the secondary armature to effect a secondary circuit change, a differem tial release relay, means for operating said impulse relay to attract its armature and hold said armature attractedduring the primary operation of the impulse relay and a neutralizing winding for said release relay effective to cause a retraction of its armature only responsive to an extended deenerforoperating said differential release relay by the neutralization of" its windings respon: sue to an extended (lecnerg1zatio1i' of the impulse relay, and a release circuit operative responsive to such operation of the release relay. f1;

11. A two-conductor control circuit for automatic switches including prin'1ary,'dif :l'erent-ial secondary and release relays, and means for controlling said relays 'over the two sides of a metallic line circuit in series. 12. A control circuit for automatic switches comprising an impulse relay, means for rapidly operating the impulse-relay for transmitting primary impulses, a difleren- 3;

ti'al secondary relay, means for operating said differential relay to attract its armatureand for maintaining said armature attracted during the primary operations of the iniiulse relay and a ncutralizin wind- 3 ing for said secondary relay ell'ectivc upon cessation of the primary operations of the impulse relay to cause a retraction of the secondary armature to effect a secondary circuit change. 1 9O 13. A control circuit for two-dimension automatic switches comprising an impulse relay, means for rapidly operating the impulse relay for transmitting primary 1mpulses, a differential secondary relay, means for operating said differential relay by the neutralization of its windings upon cessation of the primary operations of the impulse relay to eii'cct a secondary circuit change, a dillerential release relay,nicans for operating said differential release relay by the neutralization of its windings responsive to an extended decnergization of the impulse relay, and a release circuit operative responsive to such operation of the release relay."

14. A telephone system comprising a subscrihers telephone line, a two-dimension switch for extending a connection from said line having one motion for electing groups of trunk lines and a second motion for selecting an idle trunk in an elected group of trunk lines, a differential secondary relay for controlling the second of said motions,

and a differential release relay for controlling the release of said switch.

15. A metallic line control circuit for a twodimension switch comprising an impulse relay, means for operating said impulse relay for transmitting primary im- 1 pulses,'a differential secondary relay, means for operating said secondary relay uponthe cessation of primary impulses to efiect 3 secondary circuit change, a difl'erential release. relay, and means for operating said 1 5 release relay responsive to a prolonged deenergization of said impulse relay for closing a release circuit.

16. An automatic switch of the character described tor extending connections, an int 3 phone line,'an automatic switch for extendpulse relay for said switch controlled over the two sides .of a calling subscribers line in series, a differential, secondary relay respon sive to the operations of said impulse relay for effecting a secondary circuit change, and a differentially Wound release relay responsive to a prolonged denergization of said impulse relay for closing arelease circu t. r

scrihers line circuit, a two-wire automatic switch adapted to be connected to said has ,circult, an-impulse relay for sa d switch responsive to circuit changes in said telephone 'llne', a difi'erentlal relay for said switch op 17. A metallicline control circuit for an automatic switch comprising an impulse relay, means for operating said impulse relay to transmit primary impulses, a differential secondary relay adapted to maintain its armature attracted during the primary operations of said impulse relay, and a neutralizing Winding affective upon cessation of said primary operations of said impulse relay to cause a deenergization of said secondary relay to affect a secondary circult change.

18. A telephone system comprising a teleing a connection from saidtelephone line in the direction of a called subscribersline, an impulse relay for said switch responsive to circuit changes in said telephone line, a differential secondary relay responsive. to said impulse relay for controlling a secondary circuit, and a differential release relay responsive' to a prolonged deenergization of said impulse relay foreffectlng the closure of a release circuit.

1!). An automatic telephone exchange sys tem comprising a subscrlbers telephone line, an automatic selector swltch for extendlng a call from said line, an impulse relay respon- V sive to circuit changes in said telephone line, a differential secondary relay for said switch, means for operating said differential relay to attractits armature and for maintaining said armature in its attracted position during the primary operations of said impulse relay, a second Winding for said differential relay affective upon cessation of erated to attract its armatureresponsive to the first primary-operation of said impulse relay, and a neutralizing Winding for said second relay effective upon aprolonged de- 'energization 'of" said impulse relay to cause a retraction of its armature thereby effecting circult changes.

21. A telephone system including a suh-= scribers line circuit, a two-Wire automatic switch, automatic means for connecting said subscribers line circuit to saidauto'matic switch, an impulse relay for said switch,

transmitter connected in said line circuit for interrupting the circuit of said impulse re lay, thereby causing said relay to be rapidly intermittently operated, and a differential relay controllable by said impulse relay for controlling a switchingcircuit.

22. An automatic telephone exchange system Including a subscrlbers telephone line,

an automatic selector switch for extending.

a call from said line, an impulse relay responsive to interruptions of said telephone line, and a differential release relay responsive to a prolonged denergization of said impulse relay for controlling a release circuitforsaid automatic selector.

23. An automatic telephone'exchange system including-a subscribers telephone line, an automatic selector switch for extending a call from'said line, an impulse relay responsive to interruptions in said telephone line, and a. differential secondary relay controller 'ble by said impulse relay for controlling a said primary operation to cause a retraction of the secondary armature of said secondary relay, and a circuit controlled by said retraction.

20. A telephone system comprising a sub- 

